1. Field of the Invention
The present invention relates to a pressure measurement apparatus and more specifically, to an air pump pressure gauge.
2. Description of the Related Art
Many prior art designs of air pump with pressure gauge are known. Exemplars are seen.
U.S. Pat. No. 3,981,625 discloses an air pump in which a transparent handle and a piston are configured to form a pressure gauge.
U.S. Pat. No. 5,779,457 discloses a view window type pressure gauge.
U.S. Pat. No. 6,132,189 discloses an attached pressure gauge.
U.S. Pat. No. 6,196,807B1 also discloses a view window type pressure gauge.
US2002/0174723A1 discloses an electronic pressure gauge.
US2004/0001761A1 discloses an attached analog pressure gauge.
US2008/0056922A1 discloses an analog pressure gauge.
U.S. Pat. No. 4,136,560 discloses a pressure gauge.
In a conventional air pump with an analog pressure gauge, the analog pressure gauge is attached to the outside of the housing of the air pump that may interfere with the user's operation in pumping the air pump.
In a conventional air pump with a view window type pressure gauge, a small tubular passage protrudes over the outside wall of the air pump casing for accommodating the pressure gauge. Due to the limitation of the outer diameter of the air pump, the view window is small, not facilitating viewing of the readings.
In U.S. Pat. No. 4,136,560, the pressure gauge is directly connected to, for example, the air valve of the vehicle tire. Due to this installation limitation, the structural size is limited. In consequence, the pressure indication is not apparent.
The pressure value indication of U.S. Pat. No. 3,981,625 is large enough for easy reading without interfering with the pumping operation, however, it does not allow measurement of the pressure during pumping. When measuring the air pressure, the user must release the handle and wait for a certain period of time and then view the graduations on the handle. This design is inconvenient to use.